Hydrogels that undergo volumetric expansion in response to changes in their environment and their methods of manufacture and use

A method for treating a disease, deformation or disorder of a human or veterinary patient by introduction of a hydrogel polymer through the lumen of a catheter and into an implantation site within the patient's body, said method comprising the steps of:

• (A) predicting the approximate pH that will be present at the implantation site when the hydrogel is implanted;
• (B) providing a dried, expandable hydrogel that has been prepared by a process comprising the steps of,
• (i) combining at least a) an cthylenicallyunsauirated monomer or prepolymer having ionizable functional groups, b) a crosslinker and c) a polymerization initiator, to form a hydrogel polymer;
• (ii) contacting the hydrogel with a treatment solution, the pH of said treatment solution and the time and temperature of said contact being such that a) functional groups of the hydrogel become protonated and b) the resultant protonated hydrogel will, when subsequently exposed to the pH predicted at the implantation site, undergo deprotonation and expansion at a desired rate of expansion;
• and
• (iii) drying the hydrogel to from a protonated, dried hydrogel mass sized to pass through the catheter lumen;
• (C) placing the dried hydrogel mass within the catheter lumen;
• and,
• (D) positioning the catheter at the implantation site and expelling the dried hydrogel mass into the implantation site such that the hydrogel polymer becomes exposed to the pH present at the implantation site and, if the pH present at the implantation site is substantially the same as predicted in Step A, the hydrogel deprotonates and expands at approximately the desired expansion rate, said desired expansion rate being selected such that the hydrogel mass will remain sufficiently small to be retracted into the catheter lumen for at least 15 minutes following its initial exposure to the approximate pH predicted to be present at the implantation site.